Interactive toys, also generally referred to as interactive devices, are becoming more advanced. An example of such an interactive device is a remotely controllable toy character with which a user may interact as described and illustrated in the above related U.S. Patent Applications. In the above-related U.S. Patent Applications, the interactive device is also called a controllable device or a remotely controlled performer. Such an interactive device may have electronics, motors, a speaker, touch sensors, and light sensors, each of which may be used by the device when interacting with the user. The focus of the present invention is on interactive devices having light sensors.
In particular, an interactive device may have a light sensor capable of detecting the intensity of light incident upon the sensor. In an example where the light sensors represent the device's eyes, the user may interact with the device by covering and uncovering the sensors in a game of "peek-a-boo". As part of the game of "peek-a-boo," the user may cover the device's sensors (eyes). The device may audibly respond to the user's action and wait for the user to uncover the device's sensors (eyes) as part of the game. Once the device's sensors (eyes) are uncovered by the user and the device detects a change in light, the device can appropriately respond to the user as part of the game.
In such an interactive game, the device needs to respond to a user's action, such as covering or uncovering the device's sensors and causing a variation in the light intensity incident on the device's sensors. Furthermore, the interactive device needs to appropriately respond to a user's action in a wide range of light conditions and in a manner consistent with the user's expectations. However, light detecting or sensing systems may have some problems when attempting to detect relative changes in light intensities in a manner consistent with the user's expectations.
The sensitivity of a light detecting system may be limited because there may be only a very small change in the absolute light intensity. In a low light condition, such as indoors in a poorly lit room with dark walls, the detected change in absolute light intensity when covering up a device's light sensor may be very small. A light detecting system may use the absolute change in light intensity to identify whether the sensor has been covered. However, such a system may not be able to sense or detect enough of an absolute change to properly identify that the device's sensor has been covered. Thus, such a system may have a limited dynamic range for detecting light changes. The fact that covering a light sensor with a human hand typically blocks only about fifty percent of the light makes detecting changes in light intensity even more difficult.
If a light detecting system uses a static, but low threshold to determine changes in light intensity, the light detecting system may be useful in low light situations to identify a covered or uncovered situation. However, by using a given static threshold to determine changes in light intensity, the light detecting system may be limited in use and sensitivity when used in a bright light environment. For example, a typical light sensor may produce 5 microamps of ambient sensor current while uncovered indoors (in fluorescent lighting) and 5 milliamps of ambient sensor current while uncovered in sunlight. When covered by a human hand, the same light sensor may produce about 2.5 microamps indoors and 2.5 milliamps outdoors. A low static threshold used to determine changes in light intensity of 2.5 microamps may make the light sensor too sensitive in the direct sunlight. Mere shadows may be enough to make the interactive device or toy respond inappropriately. On the other hand, a higher static threshold of 2.5 milliamps may work well outdoors in direct sunlight but would likely never be crossed in the indoor, low-light situation. Therefore, using static thresholds for determining changes in light intensity can be problematic when the device is to be used in a wide variety of light conditions and environments. The use of a static threshold can also be problematic when the user expects the device to operate a certain way after the user interacts with the device (e.g., covering or uncovering the device's sensors).
While differing light conditions may pose problems for the functionality of a light detecting system, the light detecting system may also have problems presenting a visual appearance in a manner consistent with the user's expectations. In particular, a user typically expects for a sensor or sensor housing representing the device's eye to be dark or opaque. However, this can be difficult to implement because the dark material making up the sensor or sensor housing must also allow light through it to be sensed by the light detecting system. In summary, light detecting systems for interactive devices may have limited dynamic ranges, may have problems operating appropriately in a wide variety of light conditions, and may have problems meeting a user's expectations of appearance while still functioning as an effective light detecting system.
Therefore, there is a need for a system for detecting a relative change in light intensity (1) which enhances the dynamic range of the system, (2) which adapts the sensitivity of the system to the ambient light incident on the system, (3) which detects the relative change in light intensity based on a ratio of a change in sensor current relative to an ambient sensor current, (4) which provides the same absolute change in output voltage level in response to the same relative change in light intensity regardless of the ambient light conditions, and (5) having a sensor which visually appears to be dark or opaque while still being able to detect enough light to identify an uncovered or covered situation.